1. Field of the Invention
The present invention relates to a positive crankcase ventilation (PCV) system including a check valve device.
2. Description of the Prior Art
Japanese Patent Publication SHO 64-11804 discloses a PCV system which includes a PCV line connecting a crankcase of an internal combustion engine to a portion of an intake passage of the engine located downstream of a throttle valve, a PCV valve disposed in the PCV line, and an oil mist trap chamber disposed in the PCV line downstream of the PCV valve.
Also, Japanese Utility Model Publication SHO 60-178320 discloses a check valve as shown in FIG. 11 which could be used for returning trapped oil collecting on a bottom wall of the trap chamber to a portion of the PCV line located upstream of the PCV valve. The check valve 100 includes a valve body 102 having a valve head formed of elastomer and a seat member 104 which the valve body 102 resiliently contacts. The seat member 104 includes perforations 106 which are opened and closed by the valve head of the valve body 102. FIG. 12 illustrates that when a negative pressure acts on the intake passage side of the check valve 100 and the perforations 106 are closed by the valve head, portions of the elastomeric valve head of the valve body 102 protrude into the perforations 106, causing excessive deformation of the valve head. After repeated excessive deformations, a crack will initiate in the valve head and will develop to finally break the valve head. Once the elastomeric valve head breaks, the volume of PCV gas flow will increase, making the air/fuel ratio of the intake gas lean and increasing oil consumption.